In general, solid inks (also referred to as phase change inks or hot melt inks) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. A series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye, a single pigment, a mixture of dyes, a mixture of pigments, or a combination thereof.
Solid inks typically used with ink-jet printers have a wax-based ink vehicle, for example, a crystalline wax-based ink vehicle. Such solid ink-jet inks provide vivid color images. In typical systems, the crystalline-wax inks are jetted onto a transfer member, for example, an aluminum drum, at temperatures of approximately 120 to about 140° C. The wax-based inks are heated to such high temperatures to decrease their viscosity for efficient and proper jetting onto the transfer member. The transfer member is typically at a temperature of about 60° C., so that the wax will cool sufficiently to solidify or crystallize. As the transfer member rolls over the recording medium, for example paper, the image comprised of wax-based ink is pressed into the paper.
However, the use of crystalline waxes places limitations on the printing process used for conventional solid inks, particularly if the inks are used in a direct to paper application. First, the printhead must be kept at a temperature of about 120° C. which can lead to a number of problems. At these high temperatures, dyes that are molecularly dissolved in the ink vehicle are often susceptible to unwanted interactions leading to poor ink performance. For example, the dyes can be susceptible to thermal degradation, dye diffusion from the ink into the paper or other substrate, leading to poor image quality and showthrough, leaching of the dye into other solvents making contact with the image, leading to poor water/solvent-fastness. Further, for direct to paper applications it is desirable to heat the image after printing to achieve dot gain. In addition, for some substrates, the optimum spreading of the ink drops is difficult to achieve. Moreover, when the printhead is cooled and re-warmed, the resulting contraction and expansion of the ink requires a purge cycle to achieve optimum printhead performance. Particularly, the robustness (for example, smear resistance) of current inks can be insufficient for many potential applications.
Curable solid ink compositions have been proposed. Low shrinkage radiation curable solid ink compositions that can provided the advantages of handling, safety, and print quality usually associated with solid phase change inks while providing additional breakthrough performance-enabling characteristics such as compatibility with commercially available curable monomers, low jetting temperature, low shrinkage upon cooling from the melt and robustness upon curing. Curable solid ink compositions including those containing dyes and commercially resonated pigments added directly to the ink compositions have been proposed. U.S. patent application Ser. No. 12/642,538 of Marcel P. Breton, et al., filed Dec. 18, 2009, entitled “Curable Solid Ink Compositions,” which is hereby incorporated by reference herein in its entirety, describes a radiation curable solid ink composition comprising at least one curable wax that is curable by free radical polymerization; at least one monomer, oligomer, or prepolymer; at least one non-curable wax; at least one free-radical photoinitiator or photoinitiating moiety; and a colorant; wherein the components form a curable ink composition that is a solid at a first temperature of from about 20 to about 25° C.; and wherein the components form a liquid composition at a second temperature of greater than about 40° C.
While currently available ink compositions are processes are suitable for their intended purposes, a need remains for processes for formulating stable pigmented curable solid inks that show improved resistance to aggregation upon aging and reduction or elimination of settling. There further remains a need for such ink systems that can offer improved lightfastness. There further remains a need for processes and ink formulations that require less energy for manufacturing and curing. In addition, a need remains for a new type of phase-change pigmented ink compositions that exhibit desirably low viscosity values at jetting temperatures, that generate images with improved look and feel characteristics, that generate images with improved hardness and toughness characteristics, and that are suitable for a number of commonly used substrates. Furthermore, it is desirable to ensure, to the extent that toxic or otherwise hazardous compounds are used in such products, that migration, evaporation or extraction of such materials from this new type of ink be controlled or ameliorated. When used in certain applications, for example food packaging, and direct to paper printing, it is desirable to reduce the amount of, or eliminate altogether, extractable species present, for example to meet environmental, health and safety requirements.
The appropriate components and process aspects of the each of the foregoing U.S. Patents and Patent Publications can be selected for the present disclosure in embodiments thereof. Further, throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.
Currently available methods for preparing electronic devices are suitable for their intended purposes. However a need remains for an improved system and method suitable for preparing conductive structures. Further, a need remains for an improved system and method for digitally preparing conductive structures.